It is known to attach condition monitoring units to a train axle or to a bearing thereof in order to monitor parameters such as vibration, temperature and acoustic emission.
Within the automotive sector there are a plethora of wired sensors, many of which are associated with ECU (Engine Control Unit) and OBD (On Board Diagnostic) systems. These sensors are fully integrated into the vehicles infrastructure such that during the vehicles operation they have a continuous power supply. Data communications are supported by a CAN (Controller Area Network) bus. These sensor systems operate continuously to monitor their target parameters.
Locomotives and passenger carriages also have a range of sensor systems that are fully integrated, but these are generally related to safety critical functionality. However, some rail carriages, particularly those associated with freight, have no integrated sensor systems or infrastructure that could support them.
The use of wireless sensor systems on vehicles has been steadily increasing over recent times. With the advent of wireless sensor systems it is now possible to monitor the operation of more components of rotating machinery than ever before, including component areas previously considered inaccessible. Their application is often associated with rotational components such as drive shafts and bearings.
Many of these applications require wireless sensors to be located where it is impractical to have a wired power supply. While there are a number of mechanisms which can be employed to facilitate power harvesting at the site of wireless sensors, they are often not practical for a given situation and normally still have a reliance on energy storage devices such as batteries. A consideration in the design of wireless sensor systems is the time between maintenance which is frequently dictated by the life of their batteries. As a consequence, power management is an important factor in the design of wireless sensor systems because it has immediate impact on maintenance intervals.
Currently available condition monitoring solutions with permanent power sources are configured capture data continuously. However the captured data generally contain a large volume of artifacts and the measured curves reflect the curviness of the track, imperfections of the rails and other external influences. It is therefore necessary to use complex algorithms to filter the data to eliminate artifacts and to extract valuable and reliable information on the condition of the bearing from the large volume of data.
A further issue relates to power usage of the sensors included in the condition monitoring unit. Currently, the sensor is battery powered and longevity of the battery is dependent upon the time which the sensor is spent active. The problem of limited longevity of the battery has been addressed in the prior art by replacing the battery with generator means integrated in the axle box have developed a generator integrated in the axle box to meet the increasing demands of rail transportation. This problem is of particular relevance in systems wherein electronic data transmission systems where data transmission is required in shorter intervals, where high volumes of data are to be transmitted or where active sensors requiring power supply are used.
No focus has yet been placed on power saving and a technical prejudice against the idea of power saving exists because the systems are generally considered to be safety systems.
Satellite based positioning systems such as GPS navigation systems have become popular, particularly in motor vehicles. There is now a readily available range of low cost GPS devices and chipsets available. As a consequence, many automotive manufacturers have considered exploiting the technology to provide additional features for their customers. The offerings are wide and varied, ranging from the basic provision of location information through to notifying emergency services of the location and vehicle status after an accident. A popular opportunity with automotive manufacturers is associated with the provision of vehicle diagnostic information when a car goes in for a service or repair.
Systems are now being considered that will identify the nearest dealership/garage, retrieve diagnostic codes from the vehicles OBD system and send the data via mobile telephony to the garage. One example of such a system is disclosed in U.S. Pat. No. 7,142,959 B2. GPS systems are not so common with rail vehicles for some obvious reasons, but asset tracking systems based on this technology are available as disclosed e.g. in U.S. Pat. No. 6,339,397 B1.
Those automotive uses for GPS systems associated with operational/diagnostic data are primarily associated with determination of nearest appropriate facilities, or the provision of vehicle location information to enable a more centralized system to determine such.
It has further been suggested to set geo-boundaries, or GPS gates in order to provide for triggering mechanisms based on geographic locations. Examples for systems of this kind are disclosed in U.S. Pat. No. 7,319,412 B1, US2010/0156712A1. These types of systems are primarily intended for use in security related offerings, be it offender tracking or identification of the unauthorized movement of a vehicle. While these systems offer potential triggering mechanisms based on geographic location, they are used primarily to initiate messaging systems to provide limited information to higher level systems. Even when considering vehicle diagnostic information, the systems simply pass codes from an OBD system.